The invention relates to a fixing device for orthopedic applications, substantially comprising an elongated connecting rod or guiding rod, with at least two clamping members intended for clamping orthopedic pins being adjustably secured to, or being slidably mounted on said rod, and further comprising means for securing said clamping members in relation to said rod.
Such fixing devices to be mounted externally are employed for enabling fixation of adjacent bone portions or bones at both sides of a joint in relation to each other. These devices are known in a number of embodiments, e.g. with an at least partly telescopic fastening rod having at its ends the clamping members or a guiding rod onto which said clamping members have been slidably mounted. For this last-mentioned embodiment, see e.g. NL-A-1007426 in the name of applicant.
When such fixing devices are mounted across a joint, e.g. across a wrist joint at a fracture of or near said wrist joint, this will provide the most stable situation for having the fracture heal properly. At the same time, the tendons and muscles engaging the relevant joint and the area close to it will be completely immobilized, which has the result that after the time required for healing of the fracture, generally, the joint has become completely stuck and it will often take months of physiotherapy to get the joint to move properly again.
According the aspect of the invention, in this existing method of treatment, an essential improvement can be achieved if a fixing device can also temporarily offer a possibility of movement within a certain limited range in relation to the fixing position. Due to this, it will become possible, after initial healing of the fracture, to start a treatment program in which one has a patient carry out small movements of the joint one time or a number of times a day during a certain period. In this way, the joint can be prevented from getting completely stuck and no further treatment or at least no extensive treatment will be required after the fracture has healed.
Accordingly, according to the invention it is provided for, that the connecting rod or guiding rod consists of at least two parts, a coupling member having been mounted between said parts and adjusting means having been provided by which the coupling member can be brought into a rigid coupling position or a flexible coupling position. There, the coupling member is designed in such a way that in the flexible coupling position, the parts located at both sides of the coupling member can only be changed in position across a predetermined maximum range in relation to each other. Through this, it is prevented that the healing fracture can get loaded too heavily through an excessive freedom of movement of the joint concerned.
Although one coupling member can suffice, it is preferred to mount two coupling members spaced apart on the fixing device. This has the advantage, that the fixing device, which will always be at some distance from a joint, will be more able to follow the movement of the joint within the permitted flexible range of the coupling members.
According to a further elaboration it is further provided for, that the adjusting means have been executed in such a way that with the coupling member in the flexible coupling position, the flexibility of the coupling can be controlled within a certain range. Then, the flexibility of the coupling member is preferably such, that both a flexure and a change in length is possible, which, on account of the position of the fixing device in relation to the joint concerned, is of great importance. The change in length intended can be both an extension and an reduction. The ability to control the flexibility within a certain range provides the possibility of starting the therapy with very small movements and gradually enlarging them in time, depending on the healing condition of the fracture.
Further, preferably it has been provided for that a coupling member is connected to the connecting rod or guiding rod on at least one side. This provides the possibility of mounting the coupling member(s) at a desired distance from the clamping members in front of the orthopedic pins and/or at a desired mutual distance, with the help of various lengths of connecting or guiding rod.
According to a preferred embodiment, it is provided for, that a coupling member substantially comprises a connecting part being provided with at least one helical cutout across at least a part of its length, said cut-out extending to the axis of the connecting part or a recess in the connecting part, made at the level of said axis, the adjusting means being in the shape of a retaining sleeve to be mounted across the connecting part.
According to a further elaboration, it has further been provided for, that threading is mounted on the outside of the connecting part and that the retaining sleeve is a threaded sleeve. For the type of thread to be mounted, there are a number of possibilities, such as e.g. a thread having a smaller pitch than the helical cut-out, a left- or right-hand thread or a thread incorporating the helical cut-out, such as trapezium thread.